Video transducing system employing a flying spot scanner



June28, 196,0 F. P. VANAMAN ETAL 2,943,233

VIDEO TRANSDUCING SYSTEM EMPLOYING A FLYING SPOT SCANNER Filed lMay 26, 1958 4 Smeets-Sheet 1 ArrozA/EY June 28, 1960 F. P. VANAMAN ETAL 2,943,233

VIDEO TRANSDUCING SYSTEM EMPLOYING A FLYING SPOT SCANNER IIiled May 26, 1958 4 Sheets-Sheet 2 LIV bk. is

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INVENTORS fnN/ R Wma MAN C #Mmes H. 0MM

June 28, 1960 F. P. vANAMAN ETAL VIDEO TRANSDUCING SYSTEM EMPLOYVING A FLYING SPOT SCANNER Filed May 26, 1958 4 Sheets-Sheet 3 INVENTORS FRA/w( l? VHA/AMAN BY CHARLES H- 10DM /rrvzA/EY June 28,- 1960 F. P. VANAMAN EI'AL VIDEO TRANSDUCING SYSTEM EMPLOYING A FLYING sPoT SCANNER Filed May 2e, 1958 4 sheets-sheet 4 NNQ mmmHh.

INVENTOR5 FRANK R VmvAnu/v QS Nh,

H, 0 B; CHA/@1.5.5 99M United States Patent This invent-ion relates to television apparatus, and more 'particularly to a video transducing system employing a scanner of the flying spot type.

A main object of the invention is -toprovide a novelY and improved videotransducing system of the flying spot type which -is easy to operate, which may be employed to televise various kinds andsizes of `visual material, which may be easily constructed, asa substantially self-contained unit,twhich requires aV minimum "amount of auxiliary equipment, and whichmay be used to supply picture :signals to, an unlimited number of video monitors r 2,943,233 Patented June 28, 1960 ice visual material, eliminating the necessity of making copies and physicallytransporting same. The apparatus maybereadily employed in conjunction with an audio channel; so that audio information, such as live or recorded spoken comments may be transmitted simultaneously with the visual material.

The apparatus of the present invention is intended for application in a large number of activities, such as the visual transmission of commercial documents from` a centralized location to remote offices requiring same, the' transmission of educational material, the `transmission of transportation schedules and other data from communica-l tion centers, the transmission of technological information in industrial establishments, the transmission of adver tising material in large stores, the transmission of train ing material or instructions in military ornaval estab-A lishments, and the transmission of visual information in any other activity where it is desirable to convey Ysuch infomation instantaneously to a large number of receiving stations.

In general, the apparatus of the present inventionv operates as follows:l The raster on the screen of av kinescope is focussed onto lthe transparency or other representation to be transmitted; light is collectedrtherefrrom or television receivers within transmitting distance .of the f transducing system.

A further object of Ithe invention is Ytoprovide;

improved video transducing system of the flying spot. `ty'pe employing a kinescope Vas the flying spot sourceA and being provided with circuitry to protect same and to prevent Y,

burning of its screen in the event of failure of either lthe Vertical or horizontal sweep voltage thereof.

A still further object of the invention is to provide an improved video transducing system of the flying spot type which employs easily available optical components, which may be easily adapted to accommodate motion picture lm or other transparent material, which may be easily converted to televise opaque or live material, and. which may be employed to reverse negative material'so that it will be displayed in positive form;

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

Figure l is a block `diagram of an improved video trails-l ducing system constructed in'accordance with the present invention.

Figure 2 is a schematic diagram showing the electrical circuits Vof the photomultiplier tube`preampli`er, and vid'eoamplier stages of the system of Figure Y1.

Figure 2A is a schematic diagraml of a portion of the preamplifier circuit, showing a rnodcation thereof for the` purpose of reversing televised negative material an'd displaying same inpositive forrnby the` system of the present invention.

" Figures 3A and 3B are complementary schematic dia- 4 grams showing the remainingelectricalcircuitfs.of the system of Figure 1, Figure'SA'showing theldellection, synchronizing and blanking circuits andFigure 3B lshowing the high voltage and knescope protective circuits of the system. v f

A prime purpose of the4 present invention is to provide apparatus for the visual transmission of information carried on a transparency from a master station to oneor lmore remote stations. As Will be further explained, the apparatus can also be `employed'to transmit visual inand Vaccurately 4focussed by an optical system onto theA light-sensitive element of a photomultiplier tube; changes. in light value produced by the representation are trans.- lated at the output of thel photomultiplier tube as current changes flowing through a resistive load, said current changes being suitable for amplification to a usable leveli Y after amplification, Vthe resultant signals are mixedwith blanking and synchronizing signals. The resultant mixed output signals can then be fed to a video monitor for display. The mixed output signals may also be usedto modulate a radio frequency carrier Wave which mayhave the frequency'range of any standard television channel. The modulated radio frequency wavemay be applied to any unmodified televisionreceiver for display.v Y

A master monitor is employed with the transducng apparatus for the convenience of operating personnel, providing a continuous. check on the quality of the outgoing picture signal. Circuitry is included for the protection of the transducing knescope to prevent burning' of its screen in the event of failure of either the Vertical or horizontal deection voltages applied to the kinescope.A

Referring to the drawings, Figure 1 shows in block form a typical video transducing system according to the present invention. The system comprises a kinescope V25 which is suitably mounted, for example, in a vertical position .with its screen uppermost and horizontal. Kinescope V25 is provided with a gun structure including the cathode 1i, and withy focussing means, for example, the permanent-magnet focussing member 12,1'nounted ad. jacent the neck of the kinescope'. The focussing eldof the permanent magnet 12 may be adjusted as required, namely, to vary its strength, by the use of suitable magnetic shunts. The kinescope is provided with a vertical Vdeflection yoke 13 and a horizontal deflection yoke 1 4,

which may be incorporated in a conventional single-yokev assemblyl disposed on the neck of the kinescope.V The kinescope includes avhigh voltage anoderto lwhich is' conf" nectedthe output cable of a high voltageV circuit'15,'pres 'ently to be described.

formation from 4an opaque carrier to the remote stations. I

The apparatus is adapted to. transmit visual information in Written or printed form, or information in the process of being Vwritten or drawn, or other 'types of visual information, such as photographs, or`.the like.

'Said apparatusprovides instantaneous transmissioof the i Suitable means, not, shown, iis provided Ato 'supporta transparency/)716, carrying information to be transmitted, in a horizontal planeV A-A above and adjacent the screen of kinescope V25. The transparency 16 may` comprise a relatively large sheetjof theV same order of size asithe raster. on the screen. The kinescopeis preferably of substantial size and has a screen at least 10- inches in diameter, so thatthe transparency 16 may be, for example,

of ordinary lettern size.

Suitably mounted above the kinescope V25 yis a housing 17 containing the optical components of the apparatus and the photomultiplier tube VA and its associated preamplifier 18.

l A1 suitable filter-'19, for example, an ultraviolet' filter, isv mounted' on the s creen of Vkinescope V25, said filter being interposed between the transparency 16 and the screenpso as to remove undesired color components fromV the light derived from the raster on the screen and to limit. the transmitted light to the ultravioletportion ofthe spectrum.

The photomultiplier tube VA is mounted in an optical chamber 20 containing the objective assembly 21 which collects the light fromthe transparency 16 and projects it'cthroucgh condensing lenses 22, 22 to the light-sensitive element ofV the. photomultiplier tube. The housing 17 and' the optical chamber 20 are suitably slotted and are provided with .means to receive a smaller transparency 2,3,` if so desired, such as a slide or motion picture film, instead of using a large transparency 16, the light from theraster of kinescope V25 being focussed by the lens assembly 21 through the transparency 23 at the plane BL-B, as shown in Figure l, so as to be modulated thereby and is focussed on the light-sensitive element of photomultiplier tube VAl by the condensing lenses 22, 222

is displayed, providing a continuous check on the quality of the outgoing'pictureV signal.

A kinescope protective circuit 36 forms part of the transducing system and protects the yflying spot kinescope V so as to prevent burning of its screen in the event of failure of either the vertical or horizontal sweep voltages applied to the deflection yoke members 13 and 14. Aspshoyvn, the `horizontal defiection voltage" is applied at 37 to one input portion' of protective circuit 36 and the vertical deliection voltage is applied at 3S to another `input portion: of circuit 36; The protective circuit 36 controlslthe high voltage circuit 15 by an output connection 39 thereof and has another outputconnection, designated at 40, whichicontrolsa relay device' 41 arranged to control the bias voltage on the cathode 11 of kinescope V25. As will be presently described, when relay device 41 becomes energized, as a result of the failure of either the horizontal or the vertical deiiection voltage, or both, the bias'voltage on cathode 11 Ais raised to a maximum positive value, sufficient to cutoff the kinescope beam. Normal brightness of the kinescope screen is adjusted by the*Y brightness control potentiometer 42.

Referringnow'to Figure 2, it will'be seen that the outputsignalfrom theV rnain anode 43 of photomultiplier i The resultant signal developed by the photomultiplier v tube' VA isamplified in the preamplifier 18 and is further amplified in a video amplifier, shown at 24.

` The horizontal deflection voltage supplied to horizontal' yoke 14 is generated in horizontal defiection circuits, designated generally at 25, and may be synchronizedby a' horizontal synch generator, shown at 26. The vertical deflection voltage supplied to 'vertical yoke 13 is similarly generated in vertical deflection circuits, designated generally at 27, and may be synchronized by avertical synch generator 28, or alternatively, by the 60 cycle supply voltage, as will be presently explained.

Horizontal synchronizing and blanking pulses are respectively developedin a horizontal synch circuit 29 and a horizontal blanking circuit 30, the synch circuit 29l receiving its input signal from the horizontal deiiection stageZS, so as to be synchronized therewith. Said horizontal synch circuit 29 also supplies an input signal to the `high voltage circuit l5.

` The horizontalblanking circuit 30 receives its input signal from the output of the horizontal synch circuit 29.

Vertical synchronizing and blanking pulses are respectively developed in a vertical synch circuit 31 and a .vertical blanking circuit 32, the vertical synch circuit 31 receiving its input signal from the vertical deflection stage 27 so as to be synchronized therewith. The Averticalblanking circuit 32 receives its input signal from the output of the vertical synch circuit 31.

The outputs of the horizontal synch circuit 29 and the vertical synch circuit 31 are combined and are added to the videov signal in the video amplifier 24. Similarly, the outputs of the horizontal blanking circuit 30 and the vertical blanking circuit 32 are combined and are added to' said video signal in video amplifier 24.

The mixed output signal of video amplifier 24 may be fed to suitable radioV frequency carrier circuitry, `shown generally at 33, to vproduce a modulated radio frequency carrier wave of a frequency band corresponding to one of the standard television channels, so that it may be received by a conventional television receiver, and so.

that the information on the transparency 16 (or 23) Will bedisplayed on the receiver viewing screen.

The mixed output signal of video amplifier 24 is also fed `through video amplifier and monitor amplifier circuitry, shown generally at 34, by means of suitable cables to one or more remote video monitors for display. The output of the amplifier circuitryl 34 is also fed to a master monitor 35 located adjacent the video transducing sys"- teni, on the screen of which the transmitted information tubeVA is applied to the control grid of the first preamplifier tubeVB through -a coupling condenser 44. The outputsignal from tube VB is appliedto the control grid of the' second preamplifier tube VC through a peaking coil 45 and acoupling condenser 46. The output signal from the plate of tube VC', in negative form, 'is applied through coupling condensers 47 and 4S to the control gridof the first video amplifier tube V26.

To' provide a positive-going output signal from tube VC, for theV purpose of reversing televised negative material and' displaying same in positive form, `the output from tube V is taken at its cathode 49 and the cathode condenser C2 is omitted, as shown in Figure 2A. Thus, the positive-going signal at the cathode 49 in Fgure 2A is appliedfthrough a coupling capacitor 47 and theV coupling condenser 48 to the control grid of the first video amplifier tube V26. l `Connected across the input to the first preamplifier tube VBis a frequency compensation circuit comprising the parallel-connected variable condenser C1 and resistor Rh which is employed to attenuate the low frequencies to levels substantially of the same order as the high frequencies. In Figure 2, another compensation network comprising the parallel-connected cathode resistor R2 and cath'ode condenser C2 is employed to boost the high frequencies; these compensation networks are for the purpose of improving the linearity of response 4to all'the frequencies involved.

TubeVG is a plate follower, used mainly for matching the output of the preamplifier 18v to the coaxial line, shown at 50, employed `to transmit the preamplifier output to the input grid 'ofthe video amplifier 24.

The preamplifier 18 and video Iamplifier 24, as well as the photomultiplier tube VA, are energized by a substantially conventional power supply circuit including the full wave rectifier Vi and the conventional voltage regulati-ng circuit including tubes V22,- V34 and V35, as shown. Also included -is a rectifier V2 -of the 6BX7 type, connectedto provide the high negative cathode voltage approximately ,-500 volts) for the photomultiplier tube VA.

Thevideo amplier 24 includes the tube V27, which lis employed asl-an amplifier for the composite blanking signal. The blanking and synchronizing pulses are supplied yto the videoamplier 2'4 by a cable which connects to. alreceptacle 51 having the respective termin-als 1, 2 and 3'. Terminal 2 is grounded, as sho-wn. The composite blanking signal is supplied `at terminal 1 and the composite synch' signal isV supplied at terminal 3. The

.composite blanking signal is supplied to the cathode of tube Yzh ,by al Wire`53- The composite blanking signal Y anfrage@ 51.2. ,f .1 rf 7 entrb 'gris ofv tube V24, being'groundemwherebyfthe ampliedfc'omposite blanking signal' appearsA at the plate of tubeVyi 'Wi'tie same polarity as the videol signal -midis added-to the' video signal output at the plate of the amplier'tub'e V25 by a wire 55 connecting theplate of tube V27` to the plate of tube V25.

L Video ampliierjzi also includes a tube V31, which is employedfasfan amplifier in "the Vsame manner'as tube V21; and which receives the composite synchsignal across its cathode potentiometer R5, the terminal 8 of cable con- SIbeing connected tothe cathode S7 of tube V31 tliroughlfaf'resistor 58 and' a wire 5 9. The grid of tube V511i`s connected to the adjustable contact of potentiometer R5, and .thejamplid composite synch signal is supplied'from the plate of tube V31 to the'output of the fourth video ampliiier tube V30 by a wire 60 connecting the plate of tube V31 to the plate of tube V30, whereby the 'airiplifledV composite synch signal has the Ysame polarityas fand is added to the mixture of, video signal and blanking famplitied in tubes V22, V22 and V30 and appearing at "the plate of tube V30; The mixture of Video, blanking Iand synch signals is further amplified in the final tube V32 of`video amplier 24 land is made availableM 'for transmission to the radio frequency carrier circuits 33V and the closed circuit amplifier circuits 34 at the outputtenninal 61. t u

potentiometer R4 `is employed to vary the biason the cathode of `tube V28. This varies the amplitude of the composite blanking signal without affecting the video signal, whereby said potentiometer 'R1 serves `asa blanking* gain control. The potentiometer R5 serves as the gain'control for the composite synch signal. I '1 A potentiometer R6 connected between the negative wire 62 ofi'the'po'wer supply-landground has its adjustable -contactconne'cted through a resistor R2 to the com- 'mon grid 'return wire 63 `of theV video amplifier tubes V255 andV29, -to provide a'means of adjusting the D.C. bias lar peaking coils are employed inthe coupling circuits between the successive stages of fthe video amplifier 24 for the same reason.

",Referring now to Figure 3A, it willl be seen that the ,horizontal deflection circuits comprise the horizontal ossillator tubeV10, the horizcntaldiscriminator tube V12, the reactance tube V11, the horizontal discharge tube V152, the horizontal sweepoutput tube-V14, the damper tube V15, and (when an external horizontal synch generator is used) the synch coupling tube V3. This circuitry is conventional landl provides horizontal sweep Voltage in the horizontal yoke -14, which is connected to the secondary 64 -of the horizontal output transformer 65 through a circuit comprising secondary 64, horizontal yoke'14, a wire 66, a wire 67, the horizontal centering 'rheostat R2 `and the positive Avoltage supply wire 68.

fl'hepllate of .thehorizontal output tube V1.1 is fed in a conventional manner from a tap 68 on secondary 64 through the'damper tube V15, through the cathode wire 69and `the-primary'70 of transformer 65. A, supervisory circuit for the horizontalsweep voltage is proyided-comprising a coupling condenser 71, a resistor R9 and a resistor R10 connected in series between tap ,68' and'ground. This circuit is tapped atthe junction of resistors R9 and R10 by the connection ,theretoof wire 37, which is in turn connected to one cathode 80 of ya double ldiode V15 (Figure 3B).

The vertical deflection circuitry. comprises the multivibrator tube V1 and the vertical output tube` V52, and is also conventional, providing vertical sweep voltage in the vertical yoke 13, which Ais Yconnected to the secondary 73 of the vertical` output transformer .7 4 through a'circuit comprising-yoke13,.a Wire 75, secondary 73, a 'Wire 76 connected toa. xedtap .on the verticalgcentering potentiometer R11, a wire 77 connectedfto theadjustable tap of saidccntering potentiometer. AThe plate of the vertical output .tubeV5A is fedfrom Wire 67 throughV a vresistor R12 and the primary 78 of output transformer 74. AV supervisory circuit Ifor the vertical sweep voltage is provided comprising a coupling condenser 81 connected between the anode of vertical output tubeV5A --and the wire 38, which is connected in turn to the remaining cathode 83 of double diode V15 (Figure 3B).

The vertical multivibratonosc'illator comprising tube V1 may be synchronized either from an external vertical synch generator connected to terminal 84, or from the 60 cycle supply lsource connected to a terminal 85, the input grid of tube V4 being selectively coupled to either terminal 84 or terminal 85 by means of a selector switch 86 whose pole is connected to said input grid through a coupling condenser 87. The 60 cycle source may comprise the output between one ofthe lingrounded terminals 88 of the filament Winding 90 of the power transformer (Figure 3B) and ground. v

The horizontal synch circuit comprises the tubes V153, V515 and V73. A signal -from the plate of the horizontal discharge tube V13A is-made available through a condenser 91 to a Wire 92.- This signal is coupled by a condenser 93 to the grid ofthe horizontal synch amplicr tube V135. The Aamplified synch signal appears lat the .plate of tube V13B, to which is connected a wire 94. This put at the lplate of tube V515 is,transmittedthroughawire 96 anda coupling 'condenser 9'7,Y tolthe grid of tube' The .amplified horizontal synch pulse, which is positivegoing, appears at the plate of tubeV-IB, to ,which is'connectedawire 98. v `The vertical' synch circuit comprises the tubes V513, VBA Aand V711. A signal fromv the outputplate of multivibrator tube V4 is coupled through aV condenser 99 and a wire 100 to lthe grid of vertical synch -ampliier tube V513. Y The vertical synch signal at the platepf tube V53 is coupled through Va condenser 101 to the-grid of ampliiler tube VGA, and the signal from the plate of tube VGA is coupled 4through a condenser 102 to the grid of vertical synch amplier tube V711. Tubes V51; and V511 are shaping tubes biased to clip pulses so that the final pulses-Will be of suitable amplitude relative to the horizontal synchpulses. The resultant vertical synch signal, which is positive-going, appears at the plate of tube V711, which is connected to wire 9 8. Thus, the posit-ive horizontal and vertical synch pulses `are combined -at Wire 98 and Iare coupled through acondenser 104 to the composite synch Wire 105, connected to terminal 3 of the connector 51.

Thev vertical blanking circuit comprises t-he tube V8 connected as a conventional multivibrator, keyed bythe vertical synch signal in the wire 100, which is connected by a wire A106 to the input grid of tubel V8.' The signal from the output plate of tube V2` is coupled through a condenser 107 to the composite .blanking Vsignal wire 108, connected to terminal 1 Yof the connector 51.

The horizontal blanking circuit comprises the tube V9, also connected as a conventional multivibrator, keyed by the horizontal synch signal'in the wire 92, which is connected by a Wire 109 to the input :grid of tube V9. The signal from the output plate of tube V9 is coupled throughV arcondenser 110 and a wire 111 to the composite blanking signal wire 108.-

Referring now to Figure 3B, it will be'seenthat the power supply for the circuits shown in FiguresV 3A and 3B comprises the constant-voltage supply transformer 89 havingthe filament-currentsupplysecondary Winding' 90 Y the amplicd l verticall from .thesecondarywinding 113 of .transformer .391, .and the positivesgolta'ge Ywire 6 8 is .connected through .the lter-1chole1f141to one terminal of said ,lament winding. The negative wire, ,shown at 115, is .connected ,in thegusual manner to the center tap of secondary 112. Suitable iiilter condensers 1- 16 4and Y117 are connected between fwire 115 land the respective terminals of iilter choke 4114. Ncgatiue wire 115 is connected `to ground y(JIJQtlre 53A) through the :vertical centering potentiometer R11.

1 flfhe Jhighfyoltage circuit 15 for kinescope V25 com- PK'SQS '111.6 :llzbS V49, V20, Vm and Vfzz- Tube V19 S C011- nected as ;a conyentional multivibrator, vand its input grid receives horizontal,synch1pnlses vfrom the plate of horizontal :synch amplifier tube V131; through the wire 94 and .a Acoupling condenser 118. rlhe voutput of multivibrator wtube'V19 is coupled to `the .grid of the output amplier tube V20 ,through a .coupling condenser 119. Positine voltage :is .applied to the plate of output tube V25 from the .wire .16S through rheostat R2, wire 67, diode V21 and a portion of the primary `winding 121i of the conventional high .voltage .transformer 121. An inductance 122 is connected as a `dummy load across the secondany 12,3 .of -ftransfnrmer 121 to take the place of the horizontal .deflection yoke normally employed with the transformer.- The 4high alternating voltage induced -in the primary 120 'is rectified Lby a conventional high voltage rectier :tube V22, the 'high voltage output terminal 124 of jprimary 120 being connected to the anode of tube V22 and vvtherectiiied high voltage from the cathode of V'tube V22 V1being applied to the high voltage anode 160 of kinescope :V25 .through a resistor 125 and the wire 126.1 f

The ki-ncscopeprotectionlcircuit 36 comprises thecontrol tubes V16 and V12 and the double diode V18. .A portion Aof `the horizontal sweep voltage from the plate `o'fVtube V15 is fed through vwire 37 to 4the cathode 800i the double diode V13, whereby `the rectified horizontal sweep voltage appears at plate I127 and becomes a steady negative D C. potential because of the charging action of a condenser y128 connected between said plate and ground. Plate 127 is connected to the grid 129 of control tube V12 Vby a wire 130. The `amplitude of this Voltage is proportional to the amplitude of the horizontal sweep'voltagc, and when the horizontal ksweep voltage isnormal, is sufcient to maintain tube V1, at cut-off; when they negative voltage on grid 129 drops helowthe cut-off val-ue, V17 draws plate current, and for the'same reason, the screen 131 of tube V17 likewise draws current.

Similarly, a portion of the vertical deilection voltage n 'is applied to the cathode 83 of tube V12 through the wire 38. The associated plate 132 rectilies the vertical detlectionvoltage and char-ges a condenser 133 connected between plate "132 and ground, developing a steady nega- ,tive D.C. voltage which .is applied by a wire 134 to the 'grid -135 of control tube V15, maintaining said tube cut oi while the vertical de'ection voltage is normal. When the ,vertical sweep voltage drops below normal value, the negative voltage on lgrid 135 drops below cut-oirr value, allowing .the plate 136 and screen 137 of tube V to draw current.

The screens 13 1 and 137 are connected together by .a wire 139 and the plate 136 and lthe plate 138 are connected together `by .a wire 140.

fbrightness control potentiometer. 42 and a resistor 141 to grou/rid. The adjustable 'contact1'48 of potentiometer 421s connected to the positive voltage supply `W`ire67 through' a resistor 149, whereby the brightness of ,the raster `on the screen of the kinescope'rnay be adjusted in the usual manner by `adjusting the normal positive .vpltage .on lcathode 11, whereby to adjust the negative bias fon -the grounded grid 153. The upper contact '150 of relay 41 is connected directly to the positive voltage .Supply -Wre 67, whereby maximum positive voltage, of theor'der of 350 volts, is applied to cathode 11 respon- 'siv1e`to the energization `of relay 41; this occurs when either screen 131 .or 137 .draws current, whereby the kine'scope beam is automatically cut olir responsive to the dropping of either of the deflection voltages r'below respective predetermined values.

As shown, the screen 151 of the high voltage output .tube V21, is connected by wire 39 to wire 140, which in tur-n is .connected through a resistor 152 to the positive .voltage supply wire 67. kIn the absence of plate current in either tube V15 or V17, the voltage drop across resistor 152 is relatively small, whereby normal screen voltage r,exists on screen 151 of tube V20. yWhen either .plate 13.6 or 138 draws current, as a result of vthe dropping of either of the deflection voltages below a predetermined value, this current, flowing through the resistor .152, causes -a Vvol-tage drop through said resistor sui- ;cient ,to substantially reduce the voltage on screen 151 whereby the output of tube V25 drops, reducing the high voltage at vthe high voltage connector ,cable A126 accordingly, and being eifective to extinguish the kinescope beam when either of the deection voltages drops ex- :ce'ssively below its normalV value.

v .Thus, the protection circuit 36 automatically .cuts off Respective discharge resistors 141 and 142 are connected across the .condensers 128 and 133.

The winding of relay 41 is connected between the screen wire 139 and the positive voltage supply wire 67 through .a screen resistor 143 and the wire 40. The grid 153 of kinescope V25 is grounded, as shown, and is therefore negative relative .to cathode V11. Cathode 11 of `kinescope V25 is connected by a wire 144 to the arma- ,ture of relay 41. Armature `14S normally engages llower Contact 146,` which is connected lthrough the the kinescope beam' .and reduces the high voltage vapplied fthereto responsive to the =failure of either deflection voltagie, avoiding any danger of burning the kinescope Screen.

In the event of the shorting vof either ofthe control tubes V15 or V17, the same protective elects occur.

lIn a typical embodiment of the invention, the com'- ponents of the circuitry shown in Figure 2 and mentioned specifically above had the following values:

Condenser V47 mfds 40 Condenser 44 mfds .5047 Condenser C1 mmfds-- 390 to 1390 Condenser vC2 mmfds l37,() Condenser 46 mfds .047 Condenser 4S lmfds .047 Resistor R1 ohms 560 VResistor R2 do 1.00 -Resistor 54 do 447100 Potentiometer R1 do .10,000 Potentiometer R5 do 500 v'Resistor 5S do 270 vResistor R, do 15,000 Potentiometer R5 do 20 The tubes employed in the circuit of Figure 2 were as follows:

TuhefVA 1F21 Photomultiplier. 'TuberVB 6AK5. `Tube VC 6CL6. Tube V1 5R4. 'Tube V2 6BX7. YTube V26 6AH6. "Tube V27 BCS. Tube V28 `Tl1be V29 BCS. Tube V30 6BC5. Tube V31 Tube V32 "Tube V33 i- 'Iube V3.1 6AU6, Tube V35 OAZ.

' awaken? lowing values were used:

p onents of the circuitry shown in Figure 3A and Vmentioned specifically above had the following values:

i [In modified circiiitshowninFigreQA,

Condenser 71 Q mmfds-- 8.2 Condenser 95 mfds s .0047 Condenser 93- `vnf-ds .001 Condenser 91 mmfds 680 Condenser 87 Q ---Q mfds ,s .25 Condenser 99 mfdst- .1 Condenser 1011.....V mfds .047 Condenser 102 v mfds .5 Condenser 104 mfds 40 Condenser` l 97 mfds .5 Condenser 81 mfds .01 Condenser 110 mfds .0l Condenser 107 ..1 mfds .25 Resistor R9 V ohms; 100,000 Resistor R10 do 4700 Rheostat R8 do 100 Potentiometer R11 do 20 Resistor R12 do 4700 The tubes employed in the circuit of Figure A were as follows: i

.ponents of the circuitry shown in Figure 3B Aandsp'eciically mentioned above had the following values:-

5g :of periodic deflection voltage connected toV said beam 'Condenser 118 minfds-- V1,50 Condenser 119 ...Q mfds @.015 Condenser 116 f m'fds' 40 Condenser 117 mfds 40 Condenser 128 mfds .0047 Condenser 133 mfds '.'01 Resistor v141 v tmegohms l Resistor 142 'do t l `Resistor 143 i j nhms 30,000 Resistor 149 v r g do V 270,000 Potentiometer 42 n do 100,000 t Resistor147 do. 22,000 'Resistor 152 K do V 6800 he tubesf employed in the circuit of Figure were .as follows:

Tube v1, *acre =The apparatus of the present invention may be 'readily adapted for televising opaque material by projecting Vthe raster on the screen of the kindescope 'by a suitableflens system onto theopaquefmaterial" tov be `televised then collecting the light rays reflected from the material and focussing them, byrmeans of another suitable 4lens system, fonte the light-sensitive element Yof thephotomultiplier tube VA; The circuitry remains essentially the same' as above described, except that it may be` de sirable to employ a kinescope having a relatively high'in- Vstanta'nejous light spot intensity, which may therefore involve thense of a kinescope having a relatively small screen, requiring a different type of focussing thanthat above described in connection with the kinescope V25. Forexarnple,V the kinescope may employ Velectrostatic focussing, ingwhich case, an additional highvoltageDC. power supply'must be employed to provide the focussing potential, which may be of the order of 7000 volts.

While a specific embodimentof a video transducing system has been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art, ThereforeV it is intended that Vno limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

l`. In a video transducing system of the character described, a flying spot source of light comprising a kine scope provided with a screen, a cathode, a high voltage anode adjacent said screen, a grid between said cathode and anode, and means connected to said cathode, 'high voltageanode and grid and being constructed and arranged to generate an electron beam from said cathode to said screen, means normally placing a voltage on said cathode which is positive with respect to said grid but which insufficient to cut off said electron beam,v beam deection means a's'sociated with said kinescope, fa source of'periodic dee'ction voltage connected to said beam t to cause said control tube to conduct when said amplitude v,drops belowsaid predetermined value, andmeans in creasingthe positive voltage on the cathode to a value sucient rto extinguish said electron beam responsive to conduction of said control tube. p

V2. In a video transducting system of the character described, a flying spot light source comprising a kinescope provided with a screen, a cathode, a high voltage anodefadjacent said screen, a grid between said cathode and anode, and means connected to. said cathode, high voltage anode and grid and being constructed and arranged'to generate an electron beam from said cathode to said screen, means normally placing'a voltage on said cathode which is .positive with respect fto vsaid gridbu-t vwhich is insuiicient to cut oi Vsaid electron beambeam deflection mean'sassociated with said kinesc'ope, a source deflection means, anormally non-conducting control tube,

'means increasing `thepositive voltage on the cathode :to

a value suicient to extinguish said beam responsive to the conduction of said control tube, means to maintain said control tube non-conducting while the amplitude 4of* the deilection voltage is above a predetermined value, and means to cause` said control tube to conduct responsive .to the decline of the amplitude of the deflection voltage below said predetermined Value. j

3. In a video transducing system of the character described, a ying spot light source comprising a kinescope provided with a screen, a cathode, a high voltage anode adjacent said screen, a grid between said cathode o and anode, and means connectedto said cathode, high VVvoltage anode and grid and being constructed and arranged to generate an electron beam from said cathode to" said screen; means normally placing a voltage von said cathode `whiclris ,positive with respect to said. grid` but "which'isinsuicient' to cut off said electron beam, beam Matese deflection means associated with `said kinescope, a vsource of 'periodic deflection voltage connectedto saidbeam deflection means, a control tube, means kincreasing `the vpositive voltage on the cathode toa value.v suflcientv to extinguish said electron beam responsive to conduction of said control tube,means to rectify the dellectionvoltage and to Aderive therefrom a steady D.C. potential lofa magnitudelin accordance with the [amplitude of the deflection voltage, means Vapplying'said D.C. potentialto said control tube, and `means tomaintain said control tube non-conducting unless said ;D,C. potential drops below @predetermined value.

A4.v In a video transducing systemcof thecharacter described,. a ying spot light source comprising a kinescope provided .witha screena cathode, a highk voltage anode adjacent said screen, a `grid between saidycathode and anode, and means connected to said cathode, `high voltage .anode and grid and being `constructed and arranged to generate an electron beam from saidicathode 'to said screen, means normally placing a voltage on said cathode which is positive with respect to said grid but which is insutcient to cut off said electron beam, beam deilection means associated with said kinescope, a source of periodic deiiection voltageconnected to said beam deection means, a normally non-conducting control tube having a cathode, a control grid and an output anode, means increasing the` positive voltage onthe cathode toa vfalue sufficient to extinguish Asaid election beam responsivepto current flow between said,l,astn amed cathode and said output anode, means deriving a steadynegatVeZDC. voltage' in accordance withtheamph'tndeofther deflection voltage,`means to. apply sametosaid control grid said negative DSC. voltage beingcsuicientjtoprevent -current flow between said. last-named cathode ',andsaid-,output anode unless the amplitude` of the v deflection, voltage f drops helow'a predeterminedvalue.

'5.11m a video Vtransducing system of thecharacterdescribed, a'flyingspot light'sourcecomprising a kinescope provided with a screena cathode archigh Vvoltageanode adjacent said screen, and a grid betweentstaidcathode, and Vsaid anode, a high voltage ,circuitV comprising. anoutput amplifier tube, a r,tn ,ultivibraton drivingly .,copnected- ,to said output amplifier tubea step-up` transformer having its primary circuit connected to lthe ,output of. saidv output amplifier tube ,andhaving a rectifierwconnected, in: ycircuit fwith' itsrsecondarywhereby to provide rectiedhigh voltage at'the output ,ofthe rectifiengmeans connecting the,outputof'the'rectier tosai d anode, means connected to said cathode, high Vvolta-ge ,anode andsaid grid and being constructedV andl arrangedto generatean .electron beam from, said cathode to ,saidscreen,beamdcection 'means associated with said linescope, a sourceof periodic dellection voltage connected to .saidl beam -deflection means, means to derive a-,D.C. .potential inaccordance with'y the amplitude `of said deflection;voltage,..and,means 'l to,control'the,amplification of said output amplifier` .tube

in accordance with thevalueof Vsaid.D.C..'potential.

6LIn avideo transducing .system of .the ,characterV described,ca flying spot light ,source comprisinga. kinescope 'adjaoentsaid screen,and a gridbetweenasaid ,cathode and said anode, a high voltage source connectedto said anode, `beam deflection meansl asso.ciated vvith.,said kinescope, a source of. periodic deflection voltage .connected to said beamdeflection means,4 means toderive a' D.C. potentialrin accordance withdthe amplitude, of said .deflection voltage, -means ,normally placing` .al voltage Von said cathode lwhich is positive with respectto said grid, and means to l,substantially increase saidpositive voltage when` said D.C. potential decreases gbelow` a predeter- .minedvalue 7. In a video, transducingsystemof the character,` described, az'ying spot light source ,eomprisinga kinescope provided .With a? screen, a cathode, a. 11i-gh voltage y,auvaode provided. with a` screen, acathode, a high,vol t age.,anode i adiacellt Said tscreen, and asti@btweellfad-athlefnd anode, a high voltage source connected tov said anode, beam deflection means associated with said kinescope, a source of -iperiodic j=deection voltage connected to said beam deflection -means,means to -derive a D.C. potential in accordance iwith thefamplitnde of said deflection voltage,biasy voltage means: connected between said cathode and gr id and' placing@ voltage on s aid cathode whichgis positive withrespect to said grid, and means to ,simultaneously decrease the voltage from said high voltage source and substantially increase Athe positive voltage on said cathode responsive to Athe'decrease of said D.C.po tential below a predetermined value.

-8. In a video transducing system of the character described, a-fiying spot'light source comprisingta kinescope, a high voltage circuit comprising an output amplifier tube, a multivibrator drivingly connected to saidoutput tube, a step-np transformer having its primary circuitconnected to the output of said output amplifier tubeland having a rectifier connected in circuit with its secondary, whereby to provide rectified high voltage at the output of the rectifier, means connecting the output of the rectierto said kinescope, beam deflection means operativ y associated with said kinescope, a source of de'ectionpvolt- Aconnected to said beamdeflection means, andlmeans'cpntrolling saidhigh voltage circuit to regulate thenamplification of said output amplifier tube in accordance with the magnitude ofY the'y deflection voltage.

9. In a scanning system of the character described,.. a kinescope provided with a screen, a cathode, a high volt- .age anode adjacent said screen, a grid between said cathode.. and anode, means connected to saidF cathode, high voltage anode and said grid and being constructed fand arranged-to generate an electron beam fromvsaidcathode to said screen, means normally placing a volta'gelori Ysaid cathode which is positivev with respect 'to said gridbut whichlis insufficient to cut off saidV electron beam, beam deflection means associated with said kinescop'e, asource of periodic 'deection voltage connected to said beam vdeflection means, a normally non-conducting. control tube, means to maintain said'control tube non-conducting when the amplitude `of said deflection voltage is abovevra' predetermined value, Vmeans to' cause said control tube to -conduct whenv said amplitude declines .below saidlpre- `determined-.valuedand means increasing the positive voltage on:tl1e Acathode to a value sufficient toeXtinguish said electron beam responsive to conduction .,of. ls aid ycontrol tube.

l0. In a'sanning system of the character described, a kinescope provided with a screen, a cathode, ahigh'vclt- ,ageanod'e adjacent said screen, and a gridl between said cathode and anode, a high voltage circuit `comprisingan output amplier tube, a multivibrator drivingly connected to said outputrarnplier tube, a step-up transforme having its primarycircuit connected to the outputof saidoutput amplifier tube and having a rectier connected. in circuit. with itsk secondary, whereby to. provide rectified ,high voltage at the output of' the rectifier, means'fcpnnecting the output of the rectifier to said anodewr'nzeans connected to said cathode, high voltage anode andvsaid grid and `being constructed and arranged to generate an electron beam from said cathode to said screen, beam deflection means operativelywassociated with saidline- Scope, a source f periodic. @steenweg .watered to said beam deflection means,meanstoV derivefaD.C. potential in accordance withmthe amplitudeof said-deflection voltage, and meansVto/ controlwthe Yamplification 0f .Said @trilt amplr tube. in accordance withthe-yalue 0f Said DfCr PQtential- 11 lInma st zaririing Vsystemof the charaCterAdesCribed, a kinescopeprovided with ascreen, a cathode, a high voltageancde-adacent said Samen, and a, grid-between, ,Said cathode a nd:anode,y a .high voltage source cpnnectemto ,saidanoda means, .cgnttestefl .is aai@ .Gethle behaalt age connected to said beam deflection means, meansto derive a D.C. potential in accordance with the amplitude amnesia of said deflection voltage, bias voltagemeans connected Y between said cathode-and grid and placing a voltage on said cathode which is positive with respect to said grid, and means to simultaneously decrease the voltage from said high voltage source and substantially increase the positive voltage on said cathode responsive to the decrease of said D.C. potential below a predetermined value.

l2. In la scanning system, a kinescope provided with a screen, a cathode, a high Vvoltage anode adjacent said screen, a grid between the cathode `and the anode, a source of high voltage connected to said anode, and means to provide an electron beam from said cathode to said screen, means normally placing a voltage on said cathode which is positive with respect to said grid but which is insuflicient to cut oif said electron beam, beam deflection means disposed adjacent said lsinescope, a source of periodic deiiection voltage connected to said beam deliection means, means to derive a negative VD.C. potential in accordance With the amplitude of said deilection voltage, a normallyenon-conduct-ing control tube hav. ing a plate, :a screen, a control grid'iand a cathode, means applying said negative D.C. potential to said control grid, said negative potential normally being suiicient to prevent conduction ofthe control tube, means causing the control tube to conduct when said negative D.C. potential declines below a predetermned'value,` a current source,

relay means, means to increase the positive voltageon the kinescope cathode to a value suicient to cut ol said beam responsive to` energization of the relay means, means applying positive potential from said current source to the control tube plate and screen, and means connecting said relay means in circuit with said current source between said control tube'screeny and the control tube cathode to receive screen current and being'constructed and arranged to energize said relay means by the screen current of said control tube when the control tube conducts.

13. In a scanning system, a kinescope provided with a screen, a cathode, a high voltage anode adjacent said screen, a grid between the'cathode and the anode, a high voltage circuit comprising an output ampliiier tube, a

multivibrator drivingly connected to said output amplifierV tube, a step-up transformer having its primary circuit connected to the output of said ampliiier tube and having a rectifier connected in circuit with its secondary, whereby to provide rectified high voltage at the output of the rectifier, means connecting the output ofthe rectifier to said anode, and means to provide an electron beam from said cathode to said screen, means normally placing a voltage on said cathode which is positive with respect to said grid but which is insuiicient to cut oif said electron beam, beam deflection means disposed adjacent said kinescope, a source of periodic deliection voltage connected to said beam deflection means, means to derive a negative D.C. potential in accordance with the amplitude of said deection voltage, a control tube having a plate, a screen, a control grid and a cathode, means applying said negative D.C. potential to said control grid, said negative potential normally being suiiicient torprevent conduction of the control tube but allowing the control tube to conduct when it declines below a predetermined value, a current source, relay means, means to increase the positive voltage on the kinescope cathode to a value suliicient to cut oli said beam responsive to the energization of the relay means, means applying positive potential from said current source to the control -tube plate and screen, means connecting said relay means in circuit with said current source between said controltube screen and thecontrol tube cathode and being constructed and arranged to energize said relay means by the screen current of saidV control tube when the control tube conducts,

a dropping resistor connected in circuit with the'plate of the control tube, whereby a substantial drop in voltage', on the controltube plate occurs when the control tube conducts, and means controlling the Vampliiicationof said output ampliiertube in accordance with the voltage on said control tube, plate. l

References Cited inthe tile of *thispatent` UNITED STATES PATENTS 2,514,079 Lockhart July 4, 195o 2,709,768 King May 31, 1955 2,829,199 Baracket et al. Apr. l, 1958 2,860,283 Horowitz Nov. 11, 1958 FOREIGN PATENTS Y 452,730 Great Britain Aug. 28, 1936 

